The invention relates to a valve and to a use of the valve. Valves, for example for gas ducts are known. They often composed of a housing with a valve seat in which a rotatably arranged flap for closing off the gas duct is arranged. In order to avoid leakage air, the flap is provided here with a piston seal which runs around on the outside. The latter is generally composed of a metal ring which has a gap for reasons of flexibility. During operation this often results in the disadvantage that it is often impossible to close said gap completely so that leakage air escapes through said gap, which is not desirable.
FR-A-2 683 289 discloses a valve which is composed of a housing with a valve seat for a flap which is rotatably mounted on a drive shaft, in which valve a first piston sealing ring is arranged on the outside around the flap and a second piston sealing ring is arranged in a circumferential groove in the flap, which rings are each embodied as a metal ring with a first gap or a second gap which are not aligned with one another. This valve is used as a tubular seal.